Transport Across the Cell Membrane Flashcards
what is active transport
active transport is the movement of molecules or ions across a selectivley permeable membrane from a region of lower concentration to a region of higher concentration (against a concentration gradient).
Energy is required as its against the gradient.
What is the function of the cell membrane
controls the entry and exit of substances of the cell
what is diffusion
diffusion is the movement of molecules or ions from a region of higher concentration to a region of lower concentration (down a concentration gradient) across a selectively permeable membrane.
It is a type of passive transport (no energy required)
Glucose and Oxygen can diffuse into the cell and CO2 diffuses out.
Only small molecules can diffuse across the cell membrane.
what is the cell membrane made of
proteins and phospholipids - arranged in a phospholipid bi layer
what feature of a cell membrane allows certain substances through
selective permeability
describe phospholipids relationship with water
the heads (phosphate) are hydrophillic, the tails (lipids) are hydrophobic.
what is osmosis
osmosis is the movement of water from a region of high water concentration to a region of lower water concentration across a selectivley permeable membrane.
type of passive trasnport
no energy required
give an example of active transport
sodium-potassium pumps in nerve cells. The pumps are the membrane proteins.
What are the membrane proteins responsible for
active transport and osmosis
describe the effect of osmosis in a animal cell
high levels of osmosis into a animal cell will cause the cell to swell and burst, high levels of osmosis out of an animal cell will cause the cell to shrink and shrivel
describe the effect of high levels of osmosis on a plant cell
high levels of osmosis into a plant cell will cause the cell to swell and become turgid (cell stiffens but retains general shape), high levels of osmosis out of a plant cell will cause said cell to become plasmolysed (cell body peels away from cell wall)
what are the factors which affect the rate of active transport
glucose concentration
oxygen concentration
temperature (enzymes)
(these affect AT as AT requires ATP and these factors affect repiration)
what substances diffuse into a cell?
O2 and glucose (requirements for aerobic respiration)
what substances diffuse out of the cell
CO2 (waste products of aerobic respiration)
